FDA notes continuing steps to address antiparasitic resistance

Agency calls antiparasitic resistance "growing animal health threat" that can result in production losses in food-producing animals.

December 23, 2019

4 Min Read
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The U.S. Food & Drug Administration continues to work with stakeholders to address antiparasitic resistance in livestock (cattle, sheep, goats, swine and poultry) and horses.

The agency recently noted that in an ongoing effort to help maintain the effectiveness of approved antiparasitic drugs, FDA has produced two videos on antiparasitic resistance, released the results of a survey of the U.S. veterinary community about antiparasitic drug use and antiparasitic resistance in grazing animals and asked animal drug companies to add information about antiparasitic resistance to the labels of all approved antiparasitic drugs for livestock and horses.

Parasite infections are a health and welfare concern for livestock and horses. Therefore, effective antiparasitic drugs are vital to the animal health industry in the U.S., FDA said. However, parasites are becoming increasingly resistant to drugs that were generally effective against them in the past.

In these resistance situations, FDA explained that after an animal is treated with an antiparasitic drug, the susceptible parasites die, and the resistant ones survive to pass on resistance genes to their offspring.

Although antiparasitic resistance in animals doesn’t directly affect the health of people in the U.S., it’s a growing animal health threat and can result in production losses in food-producing animals, the agency said. Heavy parasite infections can cause diarrhea, weight loss, anemia (low levels of red blood cells) and death in animals.

Antiparasitic resistance also poses a significant threat to the sustained effectiveness of antiparasitic drugs.

FDA said science shows that antiparasitic resistance can’t be stopped. Parasites will continue to evolve and develop resistance; however, this natural process may be slowed down.

FDA pointed out that its strategy to address antiparasitic resistance aims to promote the sustainable use of antiparasitic drugs in livestock and horses to help slow the development of antiparasitic resistance in these animals. This, in turn, will help ensure that antiparasitic drugs remain effective for as long as possible.

FDA pointed out that within the last two years, it has taken the following actions to spread awareness about antiparasitic resistance.

It has produced two videos for animal producers and owners on antiparasitic resistance: (1) "Antiparasitic Resistance in Cattle, Small Ruminants & Horses in the U.S.," which discusses how to detect antiparasitic resistance and what to do about it, and (2) "Using Refugia to Manage Parasites in Cattle, Sheep, Goats & Horses & Reduce Resistance to Dewormers," which explains the concept of refugia and how it helps reduce antiparasitic resistance.

It has released the results of a survey of the U.S. veterinary community about antiparasitic drug use and antiparasitic resistance in grazing animals. FDA said the survey, which focused on cattle, sheep, goats and horses, collected information for the first time from U.S. veterinarians and veterinary parasitologists to find out:

* Their current level of awareness of and concern about antiparasitic resistance in grazing animals;

* Which strategies they commonly use to detect, monitor and/or manage parasites and antiparasitic resistance, and

* Their opinions about the best ways to ensure the safe and effective use of antiparasitic drugs.

FDA said it hopes the survey results will facilitate dialogue among animal drug companies, researchers, regulators, educators and animal owners regarding ways to minimize the development of antiparasitic resistance.

It also has requested that animal drug companies voluntarily revise the labels of drugs intended to treat certain internal parasites in livestock and horses to add information about antiparasitic resistance. FDA said the requested labeling changes specifically affect anthelmintics used in livestock and horses. Anthelmintics, often called dewormers, are antiparasitic drugs that treat certain internal parasites, such as roundworms. Resistance to dewormers is particularly concerning in grazing species (cattle, sheep, goats and horses) but is also a problem in swine and poultry.

The new labeling information emphasizes these important points:

* Any use of a dewormer can result in the development of antiparasitic resistance.

* Proper dosing is critical to the safe and effective use of a dewormer.

* End users should work with a veterinarian to monitor herds and flocks to determine the extent of antiparasitic resistance on a particular farm.

* Dewormers should be used as only one part of an overall internal parasite control program.

FDA made this labeling change request in December 2018 to all drug companies with approved dewormers (both over the counter and prescription) for livestock and horses. So far, FDA said more than one-third of the companies have added the new labeling statements to their products.

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